Eccentric cam structure for an automatically wound watch

ABSTRACT

A cam for mounting in an oscillating weight in an automatically wound watch has a central axis and a lateral surface which is a surface of revolution about said central axis. The fact that the lateral surface is a surface of revolution simplifies the forming of the cam. The cam is then mounted eccentrically in the oscillating weight responsible for winding the watch.

United States Patent n91 Miyasaka 51 Jan.2, 1973 [54] ECCENTRIC CAM STRUCTURE FOR AN AUTOMATICALLY WOUND WATCH [75] inventor: Mamoru Miyasaka, Nagano-ken,

Japan [73] Assignee: Kabushiki Kaisha Suwa Seikasha,

Toky0,Japan [22] Filed: Dec. 27, 1971 [21] Appl. No.: 212,245

' [30] Foreign Application Priority Data Dec. 28, 1970 Japan ..45/132712 [5 2] US. Cl. ..58/82 R [51] Int. Cl. ..G04b 5/02 [58] Field of Search ..58/182 R, 82 A; 235/105 [56] References Cited FOREIGN PATENTS OR APPLICATIONS 1,300,194 6/1962 France ..58/82 A Primary Examiner-George H. Miller, Jr. AttorneyAlex Friedman et a1.

[57] ABSTRACT A cam for mounting in an oscillating weight in an automatically wound watch has a central axis and a lateral surface which is a surface of revolution about said central axis. The fact that the lateral surface is a surface of revolution simplifies the forming of the cam. The cam is then mounted eccentrically in the oscillating weight responsiblefor winding the watch.

1 Claim, 5 Drawing Figures 1 ECCENTRIC CAM STRUCTURE FOR AN AUTOMATICALLY WOUND WATCH BACKGROUND OF THE INVENTION In automatically wound watches of conventional construction, a cam is mounted in an opening in the oscillating weight where the opening is concentric with the periphery of the oscillating weight. A shoulder which is that part of the cam on which a cam-follower rides may be concentric with the periphery of the oscillating weight but the lateral surface of the cam itself is not. As a result, cutting of such a cam is an operation difficult to carry out with the requisite precision; moreover the tools with which the operative surface of the cam is cut must continually be repositioned so that the operation is slow and the life of the cutting tools is shortened. In fact, the errors which accumulate in cutting such an eccentric cam are such that it is necessary that the operation be performed in two steps, namely the first in which the eccentric cam surface is roughly cut and a second stepin which the cam surface is finished as precisely as is possible under the circumstances. As a result, manufacturing efficiency is low, the operation is unsuitable for mass-production and costs are high.

SUMMARY OF THE INVENTION The cam of the present invention has a lateral surface which is a surface of revolution about a central axis in the cam. This makes cutting of the cam a remarkably simple operation which can be carried out with great precision. The cam is pierced by a cylindrical opening which is displaced from the central axis. The oscillating weight responsible for winding the watch has a periphery which in part is circular and has an opening therethrough which is eccentric to the periphery thereof. The opening is designed to receive the cam in a position such that the cylindrical opening through the cam is concentric with the circular part of the periphery of the oscillating weight.

Accordingly, an object of the present invention is to provide an improved cam structure which can be cut with high precision. I

Another object ofthe present invention is to provide an improved cam structure in which the lateral surface is a surface of revolution.

A further object of the present invention is to provide an improved cam structure which-is suitable for mass-production, is low in cost, and can be made with high precision.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

I The invention accordingly comprises an article of manufacture possessing the features, properties, and the relation of elements which will be exemplified in the article hereinafter described, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWING For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:

FIGS. 1 and 2 show cam structures used in conventional automatically wound watches;

FIG. 3 is vertical section taken along the line 3-3 of FIG. 2;

FIG. 4 is a cam structure in accordance with the present invention; and FIG. 5 is a vertical section taken along the line 5-5 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the prior art, a cam 3 having a cam surface 1 as shown in FIGS. l3 is mounted concentrically on an oscillating weight having a circular periphery. Cam 3 of the prior art has a shoulder 5 on which cam-follower 11 rides. Cam 3 is pierced by cylindrical hole 2 and shoulder 5 is concentric with cylindrical hole 2. Similarly, opening 4 in oscillating weight 8 is concentric with hole 2. Portion 6 is that part of cam 3 which is peened over in order to hold cam 3 within weight 8.

As is evident from FIG. 3, all parts of cam 3 are concentric with hole 2, which, in turn, is concentric with the periphery of weight 8. However the cam surface 1 is not concentric with hole 2 which gives rise to the aforenoted difficulties in achieving the required precision under conditions which permit mass-production at low cost.

In the embodiment of the present invention as'shown in FIGS. 4 and 5, all parts of cam 7 are concentric with axis line 0. Consequently it is easy to cut this cam with great precision and under conditions such as are conductive to low cost in mass-production. The hole having the axis 0 is drilled eccentrically parallel to central line 0. To complete the structure, opening 9 is cut in oscillating weight 8 eccentrically with respect to the periphery of oscillating weight 8. The displacement of hole 9 from the center of weight 8 is such that when cam 7,is placed in hole 9 in proper orientation, center line 0' corresponds with the axis ofoscillating weight 8.

It is to be noted that the entire lateral surface of cam 7 including shoulder 10 and cam-surface l2 constitute a surface of revolution around axis 0. v

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above construction without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that'the following claims are intended to'cover all of the generic'and specific fea-, tures of the invention herein described, and all state'- ments of the invention herein described, and all statements of the scope of the inventionwhich, as a matter of language, might be said to fall therebetween.

What is claimed is: I

I. An improved eccentric cam structure for an automatically wound watch, comprising a cam having a A central axis and a cylindrical eccentric opening parallel to said central axis, said cam having a lateral surface which is a surface of revolution about said central axis, a weight adapted to oscillate said cam structure, said weight having a periphery part of which is circular, and having an eccentric cylindrical opening for receiving said cam in a position such that said eccentric opening in said cam is concentric with said circular periphery of said weight and a cum-follower, said cam having a shoulder in said lateral surface on which said cum-follower is adapied to ride. 

1. An improved eccentric cam structure for an automatically wound watch, comprising a cam having a central axis and a cylindrical eccentric opening parallel to said central axis, said cam having a lateral surface which is a surface of revolution about said central axis, a weight adapted to oscillate said cam structure, said weight having a periphery part of which is circular, and having an eccentric cylindrical opening for receiving said cam in a position such that said eccentric opening in said cam is concentric with said circular periphery of said weight and a cam-follower, said cam having a shoulder in said lateral surface on which said cam-follower is adapted to ride. 